Lithium is of growing importance as an element for use in a variety of applications, particularly lithium-ion batteries. Economically viable concentrations of lithium are typically found in brines, minerals, and clays in various parts of the world. At one time, lithium production was dominated by producers utilizing spodumene and pegmatite mineral deposits found in the United States. However, South America, Australia, and China currently account for the majority of lithium production.
While hard minerals, such as pegmatite, hectorite, and jaderite, still account for a significant fraction of lithium production, the majority is recovered from brines, such as continental, geothermal, and oilfield brines. Lithium recovery is typically accomplished using natural evaporative processes. In many instances, the primary product of such brine processing is potassium, with lithium being produced as a side product.
Geothermal brines are of particular interest for a variety of reasons. First, some geothermal brines provide a source of electrical power due to the fact that hot geothermal pools are stored at high pressure underground, which, when released to atmospheric pressure, can provide a flash-steam. The flash-stream can be used, for example, to generate electrical power. In some geothermal waters and brines, associated binary processes can be used to heat a secondary fluid, which can provide steam for the generation of electricity without the flashing of the geothermal brine. Additionally, geothermal brines contain a variety of useful elements, which can be recovered and utilized for secondary processes.
It is known that geothermal brines can include various metal ions, particularly alkali and alkaline earth metals, as well as transition metals, such as lead, silver and zinc, in varying concentrations, depending upon the source of the brine. Recovery of these metals is potentially important to the chemical and pharmaceutical industries. Typically, the economic recovery of metals from natural brines, which may vary widely in composition, depends not only on the specific concentration of the desired metal, but also upon the concentrations of interfering ions, particularly silica, calcium and magnesium, as the presence of such interfering ions will increase recovery costs as additional steps must be taken for their removal.
As lithium has gained importance as an element for use in various applications, there are continuing efforts to develop simple and inexpensive methods for the recovery of lithium. In particular, there have been significant efforts in the use of layered lithium aluminates, typically of the formula LiX/Al(OH)3, such as described in, for example, U.S. Pat. Nos. 9,012,357, 8,901,032, 8,753,594, 6,280,693, 4,348,295, and 4,461,714. Unfortunately, such methods, which generally employ packed columns for the recovery, suffer from a number of drawbacks, such as shortened lifetimes due to the gradual deterioration and disintegration of the particles and collapse of the crystal structures. Lithium-manganese oxide compositions have also been used, but they tend to suffer from instability from the use of concentrated acid to recover lithium from the sorbent. There is a particular need for new compositions with enhanced lithium uptake and selectivity.